[jdk18u] RFR: 8286638: C2: CmpU needs to do more precise over/underflow analysis

[Tobias Hartmann]

Backport of [JDK-8286638](https://bugs.openjdk.java.net/browse/JDK-8286638). Applies cleanly. Approval is pending.

Thanks,
Tobias

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Commit messages:
 - 8286638: C2: CmpU needs to do more precise over/underflow analysis

Changes: https://git.openjdk.org/jdk18u/pull/168/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk18u&pr=168&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286638
  Stats: 62 lines in 2 files changed: 57 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk18u/pull/168.diff
  Fetch: git fetch https://git.openjdk.org/jdk18u pull/168/head:pull/168

PR: https://git.openjdk.org/jdk18u/pull/168